Search

The objective of the study is to evaluate the main microbiological properties of samples of raw camel milk, collected from 12 camels living in a semi-intensive system, in an arid environment in the region of Ghardaïa located 600 km south of Algiers. . These camels live under the same conditions and were selected according to age, stage and rank of lactation and the nature of their diet. Lactic bacteria have a considerable load of 1.9 104 ± 1.4 104 cfu / m. The results of the counts indicate that the mean number of total mesophilic aerobic flora (FAMT) is 7.1104 cfu / ml compared with 1.8 103 cfu / ml for total coliforms (TC) and 5.5 102 cfu / ml for thermotolerant coliforms (TTC). ). Moreover, for Enterobacteriaceae 7 102 cfu / ml (41.7% of the milks analyzed are less than 102 cfu / ml against 25% which are between 103 and 104 cfu / ml). For clostridium sulphito-reducers and faecal streptococci (SF) only 16.7% and 12.5% of our samples were respectively positive whereas only one sample was positive for staphylococcus aureus (2.8%). In contrast, all milks are free of Salmonella ssp. These results may be consistent with a good microbiological quality of the milk collected tested which would reflect the health status of these animals and the acceptable hygienic conditions during milking and transport. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the influence of vitamins, glycerol, and salts on the growth and bacteriocin production by Lactobacillus salivarius CRL 1328, a human vagina isolate, by using a chemically defined medium to determine the optimal conditions for salivaricin production. The single omission of d-biotin, thiamine, p-aminobenzoic acid, folic acid, or cyanocobalamin did not affect the bacterial growth, whereas the removal of nicotinic acid, riboflavin, and pyridoxal produced a decrease of about 30% in the growth rate. Maximum salivaricin activity was observed after the addition of 5 or 10 g/L of NaCl. On the basis of the nutritional requirements and the levels of salivaricin production, a new optimized and simplified defined medium (SDM-NaCl) for L. salivarius CRL 1328 bacteriocin production was formulated. The kinetics of salivaricin production in SDM-NaCl and in the complex media LAPTg revealed that bacteriocin production was growth linked. A combination of tricine - sodium dodecyl sulfate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE), Lumitein protein gel staining, and a bioassay for antibacterial activity indicated that the molecular mass of salivaricin CRL 1328 is about 4.5 kDa. The partially purified bacteriocin, obtained from SDM-NaCl after concentration, allowed for the design of a relatively simple method for the recovery of a biologically active protein. [ABSTRACT FROM AUTHOR]

The discovery of several healthy beneficial effects of the consumption of dairy products fermented with some bacterial strains led to the investigation of the functional properties of these microorganisms. One of the most studied properties is the cholesterol-lowering activity of bacteria with probiotic characteristics, mostly isolated from human gut. In this work, eight Lactobacillus plantarum and five Lactobacillus paracasei strains isolated from cheese were studied in vitro for their cholesterol-lowering action and their acid and bile tolerance. The ability of these strains to remove cholesterol was assessed in de Man, Rogosa and Sharpe (MRS) medium, supplied with cholesterol, and in ultra-high temperature (UHT) whole homogenized milk. Among all tested strains, two L. plantarum and three L. paracasei strains gave rise to a significant reduction of the cholesterol level inMRSbroth; in particular, L. plantarum strains lowered the cholesterol content by an average of 19.4%, whereas L. paracasei strains lowered by an average of 6.8%. The two L. plantarum strains possessing the highest cholesterol-lowering activity in MRS broth were also tested in milk. Results showed that L. plantarum strains maintained this activity because after 24 h the cholesterol decrease ranged from about 5.0% to 8.2% without significant variations between the two strains. Results from the binding assay suggested that cholesterol was mainly removed through the adsorption on the cell wall. Data from acid and bile tolerance assays showed that the L. plantarum dairy isolates were able to maintain viability at pH 2 and to grow in a medium with bile salts, and therefore were regarded as probiotics or dairy starters for new probiotic or functional food production. [ABSTRACT FROM AUTHOR]

The growth rate of the widely used laboratory strain Lactococcus lactis subsp. cremoris LM0230 was reduced if aspartic acid were present in the growth medium. The strain LM0230 is a plasmid- and phage-cured derivative of L. lactis subsp. cremoris C2, the ancestor of the original dairy isolate L. lactis subsp. cremoris NCDO712. The growth of both C2 and NCDO712 was unaffected by exogenous aspartate. Also, the growth rate of the pyrimidine auxotrophic mutants of L. lactis was affected by exogenous aspartate. The maximum observed reduction in the growth rate was ~ 35% when compared with the wild-type strain, and this varied with the concentration of aspartic acid. The observed effect of aspartate could be explained by the accumulation of the toxic pyrimidine de novo pathway intermediate, carbamoyl aspartate. Assays of the pyrimidine biosynthetic enzymes of L. lactis LM0230 showed that the partial pyrimidine requirement can be explained by a low specific activity of the pyrimidine biosynthetic enzymes. In conclusion, L. lactis LM0230 during the process of plasmid- and prophage-curing has acquired a partial pyrimidine requirement resulting in sensitivity toward aspartic acid. [ABSTRACT FROM AUTHOR]